Torpedo steering system



Nov. 13, 1962 R. H. KITTLEMAN 3,063,396

' TORPEDO STEERING SYSTEM Filed A ril 19. 1956 ,2e SERVO "*3. AMPLIFIER H 20 y y y 30 28 I COURSE RUDDER GYRO ACTU RUDDERs 32 VOLTAGE J PICK-OFF 34 COURSE RATE SWITCH R TIMER INVENTOR.

I ROBERT H. KITTLEMAN i BY j wfly ATTORNEYS 3,063,396 TORPEDO STEERING SYSTEM Robert H. Kittleman, Sharon, Pa., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Apr. 19, 1956, Ser. No. 579,410 6 Claims. (Cl. 114-23) This invention relates to acoustic homing torpedoes, .and in particular to a steering system for use therein during underwater target search.

Modern acoustic-homing torpedoes, intended princlpally for use as anti-submarine weapons, are designed to be launched from aircraft, ships or submarines toward or into the general vicinity of the enemy target as determined by sonar or other means. From that point on, however, these torpedoes must seek the submerged target submarine and detect its presence and direction before being able to execute a homing attack. In order to accomplish such detection, there may be utilized various search patterns or courses in both azimuth and depth, often in programmed combinations intended to maximize the probability of target acquisition. Such search courses, to effect acoustic scanning of a region encompassing the target, are necessary because of the directivity or narrow beam characteristic of the target-sensing hydrophone or transducer which is employed by the torpedo.

For a torpedo which is initially guided upon the basis of prelaunch information to in effect look toward the suspected location of a target submarine, with the torpedo in a state of readiness to detect and home upon the target, the type of azimuth search course which is generally used, to afford good probability of target acquisition in azimuth, is the so-called sinuous or snaking search in which the torpedo weaves to port and to starboard as it proceeds in the supposed target direction, thus probing r scanning through a wide layer of sea-water which may encompass the target submarine. In particular, snaking search patterns heretofore used by acoustic-homing torpedoes have consisted of symmetrical sinusoidal arcs or circular arcs, for example as obtained by means of equipment as described in connection with the Azimuth Steering Control System disclosed in copending patent application Serial No. 397,282, filed December 9, 1953 by David A. Cooke et al.

' It is a principal object of the present invention to provide an acoustic-homing torpedo with an improved azimuth steering system which yields a modified snaking search pattern of such nature as to improve target acquisition probability.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 illustrates the conventional type of snaking search course employed by acoustic-homing torpedoes during an underwater target search phase of operation;

FIG. 2 illustrates the improved snaking search course provided in accordance with the present invention; and

FIG. 3 illustrates a preferred embodiment and circuitry of torpedo steering equipment for effecting the improved snaking search course.

In order to provide a better understanding of the present invention and of the modified azimuth search course effected thereby, particularly with respect to resultant 3,063,396 Patented Nov. 13, 1962 mand signals of like frequency, applying the resultant signal to a servo-amplifier which correspondingly controls an actuator to deflect the torpedos course-steering rudders alternately to port and to starboard in a manner causing the torpedo to follow an essentially symmetrical sinuous course 10 along a heading 12 as illustrated in FIG. 1. The general direction or average heading 12 which the torpedo pursues is pre-selected by suitable adjustment of a synchro generator which, coupled to a directional gyroscope, serves as the pick-off means from which the course error signal is obtained. The snaking configuration of search course 10 is in this instance obtained by means of a circularly re-entrant potentiometer device having a uniformly-driven contact arm and connected to vary the magnitude and phase of an input voltage for use as the alternating turn command signal. The necessary parameters of the snaking course are of course largely a matter of engineering design, dictated by consideration of such interdependent factors as torpedo speed, turning rate, transducer beam width, and the period between transmissions of search pulses when in active pulse-echo operation rather than in passive-acoustic or listening operation.

Referring to the resultant character of the snaking search course pursued by the torpedo under control of the above arrangement, as illustrated in FIG. 1 which represents .an ideal case Without any modifying effects produced by torpedo hydrodynamic characteristics, it will be noted that the successive arcs of search course 10 are symmetrical and circular in accordance with the command signals. It will be understood that in following course 10 from point A to point B, the torpedos targetsensing transducer scans .a region lying principally to starboard, and that while proceeding to point C, substantially the same region is again scanned. In following such a course 10 between points A and C, then, say by a torpedo having a target-sensing range of 2000 feet, a snaking search cycle period of 25 seconds, a turning rate of 6 degrees per second, a speed of 30 feet per second, and a target-sensing transducer having a beamwidth of 15 degrees between its 3 db-down points, the scanned region to starboard will be approximately 1200 feet wide and the torpedo will have traveled about 350 feet in the direction 12. Similarly, incontinuing to point D, a like region lying principally to port is next scanned, and again scanned as the torpedo proceeds to point E along the snaking search course, and the torpedo will have traveled another 350 feet in the direction 12. It will be further understood, then, that while the region scanned by following a conventional snaking search course 10 may be generally thought of as a wide layer extending along the average course 12, there will in fact be areas therein of significant dimensions which remain unscanned, and other areas which are unscanned for substantially a half-period of the shaking search cycle, offering possible acquisition-escape areas for a target submarine and therefore reducing target acquisition probability.

In accordance with the present invention, an improved sinuous search course is provided by an azimuth steering control system which effects sequential port and starboard search with elimination of the immediate re-scan characteristic mentioned above, a preferred embodiment and circuitry of the said novel system being illustrated schematically in FIG. 3.

Turning first to FIG. 2, wherein it is to be understood that an acousitc-homing torpedo proceeds along the improved azimuth search course 14 in the direction 16 toward the suspected location of a target submarine, it will be noted that after scanning say a starboard area, as in proceeding along the course from point -F to point H, the

torpedo is directed to change its look direction and to next scan an area at the opposite side of the average course, in this instance in proceeding from point H to point K. It will also be observed that, as a practical matter, in changing its look direction at the point H, the torpedo is first directed to enter and proceed for a short period along the straight course H1 in direction 16 before entering upon the arcuate course JK, in order to effect a smoother transition thereto and to provide better torpedo stability without excessive roll or oscillation which would adversely affect electro-acoustic performance. It may also be noted that, in practice, with respect to the indicated abrupt changes in direction at such points as H and K, hydrodynamic characteristics of modern torpedoes will provide a further smoothing action, without substantial departure from the illustrated ideal course called for by command signals provided by equipment and circuitry such as next described.

Turning now to FIG. 3 which illustrates an exemplary embodiment of the present invention, the several components therein may be conventional per se and are therefore shown simply in schematic and block diagram form, and in a circuit which is confined to the azimuth search function and from which is eliminated the relatively complex arrangement of switching and control elements (such as described in the above mentioned copending application) which is normally employed to effect re-circuiting of the components for change over between the various phases of torpedo operation. The straight-ahead portions of the improved azimuth search course are obtained in response to course error signals supplied by the synchro generator 18 which is associated with course gyro 20, and the arcuate portions of the search course are obtained in response to turn command signals obtained from the center-tapped secondary of transformer 22. Steppingswitch 24 is employed to connect these signals, modified by summation with the course rate signals next explained, in programmed sequence to the servo-amplifier 26 which, in accordance with the resultant signals applied thereto, positions steering rudders 28 by means of the rudder actuating mechanism 30. The course rate signals, supplied by the pick-oif device 32 in response to the torpedos actual turning rate as sensed by course rate gyro 34, serve to prevent the torpedo from being over-corrected and exposed to weaving in course during the periods when the course error signals are active in the circuit, and serve to limit the port and starboard turn rates of the torpedo to a substantially fixed value during the periods when the turn command signals are connected in the circuit, these periods being controlled by the re-circuiting action of stepping-switch 24. Stepping-switch 24 in the illustrated embodiment is of conventional ten-position type controlled by a switch timer 36 which is designed to effect energization of stepping-switch coil 38 at 1.25-second intervals and to correspondingly step switch-arm 40 at like intervals, say in a clockwise direction as indicated. It will be understood, therefore, that switch arm 40 will dwell on each contact for substantially 1.25 seconds and, for the illustrated circuit connections, will provide oncourse runs of 2.5-second duration, and port and starboard turns of S-second duration. Prior to launching the torpedo, course gyro 20 is caged, brought up to and maintained at operating speed by conventional means (not shown), and uncaged to operate as a directional or free gyro. Rotor 42 of synchro generator 18 is excited from a suitable A-C source as indicated. It should be noted at this point that the input or reference A-C signals required by various components of this steering circuit, for example as required by servo amplifier 26 to serve as a phase reference therein for dervation of actuator controlling signals, and applied as indicated in FIG. 3, are to be understood as most conveniently supplied from a single source, in this instance from the AC source 44 to which primary 46 of transformer 22 is connected. This A-C source may, of course, be of three-phase type and also utilized to power the electronic equipment and the switch timer and gyroscope motors. Returning to consideration of synchro generator 18, rotor 42 is coupled to the outer gimbal of course gyro 18 and after gyro-uncaging is therefore automatically controlled as to angular position relative to stator 48, in accordance with torpedo direction. While the torpedo is still in the launching rack or firing tube, stator 48 is initially so adjusted, for example by means of a remote synchro control transformer in a servo system as described in the previously mentioned copending application, that the course error signal will assume zero value for a pre-selected torpedo heading. When in the modified snaking search phase after launching, therefore, and for an initial condition of steppingswitch 24 as shown in FIG. 3, the signal applied through leads 50, 52 to servo amplifier 26 is a course error signal, of magnitude and phase dependent upon deviation of the torpedo direction from the pre-selected heading, modified by summation with a course rate signal proportional to the torpedos actual turning rate, if any. The rudders are correspondingly controlled to turn the torpedo (and stator 48 relative to rotor 42) in a direction to reduce the magnitude of the course error signal delivered by synchro 18 until it becomes zero when the pre-selected heading is reached. The torpedo will thus seek and maintain the pre-selected heading 16, say from F to G as shown in FIG. 2, a distance corresponding to the product of torpedo speed and the 2.5-second total dwell period of switch-arm 40 upon the two connected contacts 54 of the stepping-switch. When switch-arm 40 is next stepped to dwell on the four connected contacts 56, the signal applied through leads 50, 52 to servo amplifier 26 is a turn command signal supplied by secondary section 58 of transformer 22, modified by summation with the course rate signal delivered by pick-off 32.

The torpedo will, of course, turn at a rate such that the oppositely-phased course rate signal is substantially equal in magnitude to the turn command signal. During this 5-second period, then, the torpedo pursues an arcuate course, say to starboard over the path G to H as shown in FIG. 2, and at a turn rate of say 7.5 per second Where it is desired to accomplish a search sweep of the same extent as for the conditions previously mentioned under discussion of the FIG. 1 search course. In similar manner, the torpedo next enters and continues along the onbearing course HI, and then upon the arcuate port course JK in response to the oppositely-phased turn command signal supplied by secondary section 60 of transformer 22, and repeats the complete search cycle until acquisition of a target submarine induces a circuit change-over (not shown) to initiate an attack condition.

It will now be apparent that instead of re-scanning suspected target areas which have already been searched, as in following a conventional snaking or sinuous search course as previously mentioned, the novel search system herein described provides a modified snaking search course wherein, after the torpedo has entered an arcuate course and reached a pre-determined maximum search angle to one side of a pre-selected heading while proceeding therealong, it immediately returns to the pre-selected heading, and then enters an arcuate course to the other side of said heading, repeating this cycle continuously until target-acquisition occurs.

It will now also be understood that the novel system here disclosed yields a modified and improved snaking search course of particular utility to acoustic homing torpedoes which must employ a sweeping search phase of operation. As compared to the conventional snaking search course illustrated in FIG. 1, the above-described system enables target-acquisition at an earlier point in the search run, since the run distance for a complete sweep cycle is of considerably shorter duration for like conditions. Similarly, the improved azimuth search system effects scanning of marginal areas which previously afforded acquisition-escape channels. Further, where desired, the

disclosed system can be designed to effect searching of a considerably wider area than heretofore, for a sweep cycle of the same duration as normally employed by conventional snaking search systems.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. The combination, with a propulsive torpedo requiring a sweeping-search course for electro-acoustic acquisition of a target, of course-rate gyroscopic means for controlling the steering of the torpedo along substantially continuously arcuate turns which successively alternate in direction relative to a pre-selected heading, and course gyroscopic means for controlling the steering of the torpedo along said pre-selected heading in transition runs between said arcuate turns.

2. The combination, with a propulsive craft having course-steering means, and a servo amplifier and actuator adapted to control said course-steering means in accordance with steering command signals applied to said servo amplifier, of means providing a course error signal adapted to serve as a steering command signal to efiect steering of said craft along a pre-selected heading, means providing first and second signals adapted to serve as steering command signals to effect steering of said craft in resepectively opposite and substantially continuously arcuate turns away from said pre-selected heading and at a predetermined angular rate, and means for applying said course error and said first and second signals to said servo amplifier in a repetitive sequence eflective to steer said craft in alternately opposite and substantially continuously arcuate turns, for like predetermined periods, and along said pre-selected heading in a relatively short transition period following a maximum angular excursion in each said arcuate turn.

3. The combination, with a propulsive craft having course-steering means, and a servo amplifier and actuator adapted to control said course-steering means in accordance with steering signals applied to said servo amplifier, of means providing a course error signal adapted to serve as a steering signal to eifect steering of said craft in a direction along a pre-selected heading, means providing left and right turn command signals, means for modifying said turn command signals, by summation with signals corresponding to actual turn rate experienced by said craft, to serve as steering command signals to effect steering of said craft in respectively opposite arcuate turns away from said pre-selected heading and at a predetermined angular rate, and means for applying said course error and modified turn command signals to said servo amplifier in a repetitive sequence effective to steer said craft in alternately opposite arcuate turns, for like predetermined periods, and along said pre-selected heading in a relatively short transition period following a maximum angular excursion in each said arcuate turn.

4. The combination, with a propulsive craft having course-steering means, and a servo amplifier and actuator adapted to control said course-steering means in accordance with steering signals applied to said servo amplifier, of means providing a course error signal adapted to serve as a steering signal to effect steering of said craft in a direction along a pre-selected heading, means providing left and right turn command signals, means for modifying said turn command signals, by summation with signals corresponding to actual turn rate experienced by said craft, to serve as steering command signals to elfect steering of said craft in respectively opposite arcuate turns away from said pro-selected heading and at a predetermined angular rate, and stepping-switch means for applying said course error and modified turn command signals to said servo amplifier in a repetitive sequence effective to steer said craft in alternately opposite arcuate turns, for like predetermined periods, and along said pre-selected heading in a relatively short transition period following a maximum angular excursion in each said arcuate turn.

5 For use in a propulsive craft having course-steering means, and a servo amplifier and actuator adapted to control said course-steering means in accordance with steering signals applied to said servo amplifier, steering-signal apparatus comprising means providing a course error signal adapted to serve as a steering signal to effect steering of said craft in a direction along a pre-selected head ing, means providing left and right turn command signals, means for modifying said turn command signals, by summation with signals corresponding to actual turn rate experienced by said craft, to serve as steering command signals to effect steering of said craft in respectively opposite arcuate turns away from said pre-selected heading and at a predetermined angular rate, and means for applying said course error and modified turn command signals to said servo amplifier in a repetitive sequence effective to steer said craft in alternately opposite arcuate turns, for like predetermined periods, and along said pre-selected heading in a relatively short transition period following a maximum angular excursion in each said arcuate turn.

6. For use in a propulsive craft having course-steering means, and a servo amplifier and actuator adapted to control said course-steering means in accordance with steering signals applied to said servo amplifier, steering-signal apparatus comprising gyroscopic means providing a course error-signal adapted to serve as a steering signal to effect steering of said craft in a direction along a pre-selected heading, means providing left and right turn command signals, gyroscopic means providing course-rate signals corresponding to tum-rates experienced by said craft, means for modifying said turn command signals by summation with said course-rate signals to serve as steering command signals to effect steering of said craft in respectively opposite arcuate turns away from said pre-selected heading and at a predetermined angular rate, and means for applying said course error and modified turn command signals to said servo amplifier in a repetitive sequence effective to steer said craft in alternately opposite arcuate turns, for like predetermined periods, and along said pre-selected heading in a relatively short transition period following a maximum angular excursion in each 'said arcuate turn.

References Cited in the file of this patent UNITED STATES PATENTS 1,131,563 Leon Dec. 15, 1914 1,351,526 Lees et al Aug. 31, 1920 1,401,628 Meitner et a1 Dec. 27, 1921 2,341,287 Pookhir et a1 Feb. 8, 1944 2,716,957 Kent Sept. 6, 1955 FOREIGN PATENTS 4,032 Great Britain -Mar. 15, 1915 

